THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



\ 



SEPTEMBER 1911. 



XXXVII. The Age of the Earth. Dg J. Joly, F.R.S* 



[Plate III.] 



HPHE recent contributions to the data bearing on the 

 Ji subject of the age of the earth have strengthened the 

 evidence derived by two very different methods of compu- 

 tation ; that based on the study of solvent denudation and 

 that based on the accumulation of radioactive waste-products 

 in minerals. While the indications of both lines of inquiry 

 seem individually rendered more definite by these advances, 

 the divergence in their final results have, if anything, 

 become intensified. I propose in the following pages to 

 review the opposing methods, as briefly as the many details 

 permit, and to discuss the possibility of reconciliation. 



I. The Age of the Ocean derived from Solvent Denudation. 



Three recent contributions to this subject have appeared : 

 That contained in Professor Sollas' Presidential Address to 

 the Geological Society of London, 1909 ; in a paper on 

 "A Preliminary Study of Chemical Denudation/' by F. W. 

 Clarke (Smithsonian Miscellaneous Collections, vol. lvi. June 

 1910); and in one by G. F. Becker on "The Age of the 

 Earth" (Smithsonian Miscellaneous Collections, vol. lvi. 

 June 1910). 



* Communicated by the Author. 

 Phil. Mag. S. 6. Vol. 22. No. 129. Sept. 1911. 2 B 



